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-   -   .223 1 in 7 twist ammo suggestions? (https://www.huntingnet.com/forum/reloading/226705-223-1-7-twist-ammo-suggestions.html)

Bullet Hole Bailey 01-24-2008 07:14 PM

RE: is the deal still on babe!
 
ok....well im gonna have to test these out a bit more before i decide for sure.....

93Oregongirl 01-24-2008 09:02 PM

RE: is the deal still on babe!
 
well how about our date BHB :)

eldeguello 01-29-2008 07:07 AM

RE: .223 1 in 7 twist ammo suggestions?
 
1 in 7" means that the barrel's rifling will cause the bullet to rotate one time in every seven inches of forward travel. Required twist is determined by BULLET LENGTH instead of weight-supposedly, a heavier bullet is longer, but not always. A stubby round-nose or blunt bullet can be heavier than some lighter ones that are streamilned. Length of the bullet determines the twist rate required to keep them flying point-forward!

For example, a bullet with a boat-tail must spin faster than a flatbase one of otherwise identical shape & size-the boattail making the one longer than the other. I had a .222 Remington with a 1/14 twist that shot 55-grain flatbase bullets into 0.5 MOA, and 55-grain boatails into about 4"!

Use the Greenhill formula to calculate the needed twist:

150 divided by thebullet length IN CALIBERS equals the required twistrate IN CALIBERS.

Let's sayyou have a .224", 75-grain bullet 4.5 calibers long (1.008"). 150/4.5= 33.33 So, therate of twist needs to beone turn in 33.33 calibers. Your caliber is .224", so 33.33 X.224 = 1 turn in 7.46". In this example, the bullet MIGHT be stabilized by a 1/8" twist. but will definitely work OK in a 1/7" twist. It would be on the very ragged edge of instability in a 1/9" twist. MV does help somewhat in stabilizing bullets fired in too-slow a twist, but not very much! I'd rather have a bullet spinning too fast ("overstabilized") than too slow. Usually. a bullet that keyholes when it strikes the target is spinning too slowly.


Bullet Hole Bailey 01-29-2008 11:37 AM

RE: .223 1 in 7 twist ammo suggestions?
 
wow.....so could you do those calculations with a 55 grain?

Thanks!

eldeguello 01-30-2008 08:11 AM

RE: .223 1 in 7 twist ammo suggestions?
 

ORIGINAL: Bullet Hole Bailey

wow.....so could you do those calculations with a 55 grain?

Thanks!
I can do it for ANY bullet that tickles you. Just tell me how LONG it is, and it's diameter. Weight, as I mentioned is not pertinent to determining the required twist. For example, a .30-caliber bullet, 1" long, needs a twist of1 turn in 14.22" to stabilize it,whether it is a lead bullet weighing 180 grains or a zinc bullet weighing25 grains..............

Bullet Hole Bailey 01-30-2008 09:59 AM

RE: .223 1 in 7 twist ammo suggestions?
 
ok THANKS!

ill have to measure one of them!

Bullet Hole Bailey 01-30-2008 10:14 AM

RE: .223 1 in 7 twist ammo suggestions?
 
ok....well i measured one and it was 11/16"

idk if you can do it with a fraction but i couldnt find my good set of calipers.......


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